1. Field of the Invention
This invention relates to a new and novel steerable towing device adapted to be interconnected between a towing means, such as for example, a towing vehicle having spaced two ball hitches, and a towable load, such as for example, a conventional two wheel trailer or tandem steerable four wheel trailer. In addition, this invention may be used in a steerable four wheel trailer wherein the steerable towing device functions as the front axle of the trailer. The four wheel trailer is likewise connected to a towing means through a spaced two ball hitch. During pulling by a towing means, a trailer experiences movement in directions generally referred as yaw, pitch and roll.
2. Disclosure of the Prior Art
It is known in the art to utilize a steerable wheel assembly in a tow dolly or steerable trailer.
U.S. Pat. No. 2,450,215 (Wilson) discloses a dolly for trailer which has a "V" shaped axle and steering assembly, which steering assembly is controlled by a steering crank having an acute angle between the arms of the steering crank. The towed vehicle loading point is forward of the center line of the wheels and behind the pivot point of the steering crank.
U.S. Pat. No. 3,613,921 (Ryden) discloses a tow dolly for wheeled vehicles. The tow dolly is formed of a chassis having a pair of towed vehicle wheel ramps, surge braking and linked steering mechanisms for turning the two dolly wheels. The steering mechanism has a bell crank formed of two arms of unequal length and having a 90.degree. angle therebetween. The long arm is responsive to a steering arm connected to the towing vehicle and the short arm directly moves a tie rod between the wheel steering assembly.
U.S. Pat. No. 3,876,240 (Watson) discloses a steerable four wheel trailer to be pulled behind a towing vehicle having a two ball hitch. The trailer steering mechanism has a bell crank formed of two arms of unequal length having a 90.degree. angle therebetween. The long arm of the bell crank is connected to a steering arm extending from the towing vehicle. The short arm of the bell crank is connected to a connecting rod forming part of the steering assembly of the trailer. The pivot point of the bell crank is located between the center line of the axle towards the towing vehicle. Based on the geometry of the disclosure of Watson, during a left or right turn, the steering assembly functions only to turn both wheels in exactly the same arc of rotation and keeps both wheels parallel to each other at all times. There is no loading point on the front axle, but rather a trailer is directly fixedly connected to the front axle by leaf springs and shock absorbers.